tree-wide: Remove unnecessary SIGCHLD blocking

Now that sd-event doesn't insist on blocking
SIGCHLD anymore when watching for process exit,
let's stop blocking SIGCHLD tree-wide where not
required anymore.

src/sysupdate/sysupdate.c

@@ -23,7 +23,6 @@
 #include "path-util.h"
 #include "pretty-print.h"
 #include "set.h"
-#include "signal-util.h"
 #include "sort-util.h"
 #include "specifier.h"
 #include "string-util.h"
@@ -1877,9 +1876,6 @@ static int run(int argc, char *argv[]) {
         if (r <= 0)
                 return r;
 
-        /* SIGCHLD signal must be blocked for sd_event_add_child to work */
-        assert_se(sigprocmask_many(SIG_BLOCK, NULL, SIGCHLD) >= 0);
-
         return sysupdate_main(argc, argv);
 }